Method of protecting butt joints of plate molds for continuous casting

ABSTRACT

In a plate mold for continuous casting the gaps which may be formed at the butt joints between the longitudinal and transverse mold walls due to thermal expansion are sealed by covering the joints and the areas of the mold walls immediately adjacent the joints with a thin layer of protective material.

United States tent 1191 [111 3,736,977 Stockinger [4 1 June 5, 1973 [54]METHOD OF PROTECTING BUTT [56] References Cited JOINTS OF PLATE MOLDSFOR 5 Inventor; w Stocking", 700 "r 1,611,020 12/1926 Gathmann ..249/114 Sweden 5 2,591,858 4/1952 Ostendorf ....249 s2 2,825,947 3/1958 Goss"164/73 [73] Assignee: Concast AG, Zurich, Switzerland 22 Fil d; Man 241971 Primary ExaminerR. Spencer Annear k pp No: 127,838 Attorney Sandoe,Nelll, Schottler & W1 strom [57] ABSTRACT [30] Forelgn Application PnomyDam in a plate mold for continuous casting the gaps which Mar. 26, 1970Sweden ..4596/70 may be formed at the butt joints between thelongitudinal and transverse mold walls due to thermal expan- U-S- ignare sealed covering the joints and the areas Of [51] Int. Cl. ..B22dll/02 the mold walls immediate] ad'acent the joints h a y J [58] Fieldof Search ..164/14, 73, 121, thin layer f protective materiaL 5 Claims,1 Drawing Figure METHOD OF PROTECTING BUTT JOINTS F PLATE MOLDSFORCONTTNUOUS CASTING This invention relates to a method of covering andprotecting the butt joints of plate molds used for continuous casting.

The mold cavity of such molds is enclosed by longitudinal and transverseplates, preferably made of copper. The transverse plates are usuallyclamped between the longitudinal plates and butt joints are formedbetween the side edges of the transverse mold walls and the surfaces ofthe longitudinal mold walls. Butt joints are also formed when the moldplates themselves are subdivided.

During casting with such molds differential thermal expansion of thecopper plates may result in the formation of gaps at the butt jointsbetween the copper plates. When this occurs, freshly poured metal maypenetrate into these gaps and solidify therein, and the solidified shellof the continuous casting that is in the course of being formed may bedamaged. This may lead to a metal breakout.

Furthermore, when a mold is being filled with molten metal at thebeginning of the casting operation the rising level of the molten metalmay cause a temporary differential thermal expansion of the mold wallswhich forms temporary gaps at the butt joints. These temporary gaps willtend to close after molten metal in the mold has reached its intendedlevel and has thereby restored thermal equilibrium in the mold.Meanwhile,

however, the penetration of molten metal into such temporary gaps isparticularly undesirable because it prevents these gaps from closingwhen thermal equilibrium is restored.

It is known in the prior art to fill existing gaps at the butt joints ofplate molds for the continuous casting of steel with plastic material.However, this procedure can be applied only after some castings havealready been completed and after gaps have been formed which are visibleat the butt joints. Furthermore, the location of gaps which do not formuntil after the mold is being filled with molten metal cannot bepredicted, and such gaps cannot be protected by this method against theentry of molten metal. Moreover, use of this conventional method islikely to cause additional distortion of the mold walls and furtherenlargement of the gap due to thermal expansion of residues orincrustations of the plastic material in the gap. Such increase in thesize of the gaps increases the wear on the mold plates and requirestheir replacement after a relatively short casting time.

Such conventional methods seek to repair damage which has occurred. Itis the object of the present invention to provide a method of preventingsuch damage from occurring. This is done by preventing molten metal fromentering into gaps that are likely to open up during continuous castingat the butt joints of plate molds by covering those joints which facethe mold cavity with a thin layer of protective material before thepouring of metal begins.

This thin layer does not penetrate into the joint or gap as in theconventional method, but covers the joint, extending lengthwise thereof,and also covers a narrow area of the surface of each abutting mold plateimmediately adjacent the joint.

This method prevents damage to the frozen shell of the solidifyingcasting and greatly reduces wear on mold plates. Thereby it increasesthe number of heats that can be cast in one mold before replacement orrepair becomes necessary.

These thin covering layers may consist of various materials and may beapplied in different ways. For instance, the regions immediatelyadjacent the butt joints can be coated with a liquid material such as alacquer or varnish having high surface tension to prevent it frompenetrating between the abutting surfaces. The liquid material shouldharden quickly to permit a rapid sequence of castings, and it must alsoretain a certain degree of flexibility after it has hardened. Suitableliquid materials of this nature are generally known as, for example,cellulose ester varnishes, or ZAPON- varnishes or two-componentsynthetic resin varnishes. The liquid material may be applied with abrush and may cover the butt joint between two'mold plates and a stripof about 1 cm wide on the surfaces adjacent each side of the joint.

Alternatively an adhesive tape may be used as the protective materialwhich covers the joint. Such tapes are very easy to handle and thejoints can be covered with them cleanly and quickly with a minimum ofwork. Such tapes are preferably about 2 cms wide. They cover the jointover the full length of the joint and adhere to the surfaces of thewalls immediately adjacent the joint. Such tapes may consist forinstance of a highmelting-point alloy provided with an adhesive coating.

However, adhesive tape which is bumed or melted away by the rising levelof molten metal when the mold is first filled may also be used. Such atape could be made of synthetic material. When using such tapes,splashing metal is kept away from any existing gaps by the tape. As thelevel of the metal pool in the mold rises, particularly when castingsteel, local thermal expansion of the mold walls which may be causedthereby tends to temporarily close such existing gaps. However, sinceboth the steel and any other material are also prevented from enteringsuch gaps they can be closed without causing distortion of the moldplates. The tape which adheres to the water-cooled copper platescarbonizes slowly below the level of molten metal, and providessufficient time for thermal equilibrium to be restored and for theformation of an adequately thick frozen shell on the casting. Theplastic tape which is located above the level of molten metal in themold does not burn because of the cooling effect of the mold plates andit therefore continues to provide protection against splashing metal ascasting continues.

Instead of combustible tape a metal tape may be used which is melted bythe rising level of molten metal in the mold. Such combustible ormeltable tapes do not decrease the heat transfer from the casting to themold plates.

In new molds in which the joints are fitted tightly the thin protectivelayer ensures that gaps which may open due to temporary thermalexpansion when the mold is being filled with molten metal are kept freeof metal so that they can reclose after the molten metal has risen tothe desired level.

However, it is also feasible to replace the adhesive tapes by stretchinga strip-shaped metal foil over the joints which neither burns nor melts.

A preferred embodiment of the invention is shown in the accompanyingdrawing in which the single FIGURE is a plan view of one end of atypical plate mold.

Referring to the drawing, the mold comprises a rectangular mold frame 1,within which are mounted parallel longitudinal mold plates 2, 2' whichare spaced apart by transverse mold plates 3, only one of which isshown. As shown, the end surfaces of the transverse plates 3 abut thesurfaces of the longitudinal plates 2, 2' to form butt joints 4, 4'.These'joints are each protected as previously described by a layer ofprotective material 5, 5 such as a layer of varnish or adhesive tapewhich covers the joint and extends lengthwise of the joint and extendslaterally over an area of the surface of each abutting mold plateimmediately adjacent the joint. In such molds it is conventional toprovide means such as'screw 6 to adjust the transverse plate 3, and thepressure foot 7 to apply pressure to hold the transverse plate 3 betweenthe lontidudinal plates 2, 2.

I claim as my invention:

1. The method of protecting a butt joint of a plate mold havinglongitudinal and transverse abutting mold covering the joint beforebeginning the pouring of metal into the mold with a layer of protectivematerial having a thickness not substantially in excess of that of ametal foil, said layer extending lengthwise of the joint and coveringthe joint and extending laterally over an area of the surface of eachabutting mold plate immediately adjacent the joint.

2. The method of claim 1 in-which the joint is covered by an adhesivetape which adheres to the surface of each abutting mold plateimmediately adjacent the joint.

3. The method of claim 2 in which the adhesive tape burns or melts awayin the regions covered by molten metal as the mold is filled.

4. The method of claim 2 in which the adhesive tape consist of ahigh-melting-point alloy.

5. The method of claim 1 in which the joint is covered by a liquidmaterial having a surface tension sufficient to prevent penetration intothe joint.

UNITED STATES PATENT @FFECE QETEMCATE QREQEN Patent No. 3 736 977 DatedJune 5 1.973

Inventor(s) Walter Stockinger It is certified that error appears in theaboveidentified patent and that said Letters Patent are hereby correctedas shown below:

On the title page, item "I301", cancel "Sweden" and insert--Switzerland-.

Signed and sealed this 7th day of Hay 1971;.

(SEAL) Attest:

H WARD I LFLETChEMJH. G. MARSHALL ,DANN Attesting Officer Commissionerof Patents FORM PC4050 uscoMM-oc 60376-P69 fl' U.5. GOVERNMENT PRINTINGOFFI CE I989 O366-334.

1. The method of protecting a butt joint of a plate mold havinglongitudinal and transverse abutting mold plates used for continuouscasting which comprises covering the joint before beginning the pouringof metal into the mold with a layer of protective material having athickness not substantially in excess of that of a metal foil, saidlayer extending lengthwise of the joint and covering the joint andextending laterally over an area of the surface of each abutting moldplate immediately adjacent the joint.
 2. The method of claim 1 in whichthe joint is covered by an adhesive tape which adheres to the surface ofeach abutting mold plate immediately adjacent the joint.
 3. The methodof claim 2 in which the adhesive tape burns or melts away in the regionscovered by molten metal as the mold is filled.
 4. The method of claim 2in which the adhesive tape consist of a high-melting-point alloy.
 5. Themethod of claim 1 in which the joint is covered by a liquid materialhaving a surface tension sufficient to prevent penetration into thejoint.